Image forming apparatus having a transfer member

Abstract

An image forming apparatus includes an image member, for example, an endless web photoconductor, and a transfer member, for example, a transfer drum. The endless web is driven by a frictional engagement with a drive roller. A web drive output roller fixed to and rotatable with the drive roller in turn drives an idler roller which drives a drive belt positioned around the idler roller and a transfer drive member. The transfer drive member is fixed with respect to the transfer drum and rotates the transfer drum. The outside diameter of the transfer drive member is maintained equal to that of the transfer drum despite varying ambient conditions, by employing similar materials, for example, employing a similar thickness of polyurethane as the outside layer of the transfer drive member. Thus, the peripheral speed of the transfer drum stays the same as the image member despite a varying outside diameter of the transfer drum as ambient conditions vary.

We claim: 
     
       1. Image forming apparatus comprising: an endless web image member movable at a speed through an endless path,   a transfer drum having an outside transfer surface rotatable through transfer relationship with said image member and having at least one layer of material which causes the diameter of the transfer surface to vary in response to varying ambient conditions,   a rotatable drive member, fixed to or integral with said transfer drum, which drive member has a drive surface of the same diameter as the transfer drum and a layer of material of substantially the same thickness and respense to ambient conditions as said at least one layer of the transfer drum to vary the outside diameter of the drive surface the same as the variance in the outside diameter of the transfer drum in response to varying ambient conditions,   first drive means movable through an endless path for engaging and frictionally driving the drive surface of said rotatable drive member, and   second drive means for driving said first drive means at the same speed as said image member.   
     
     
       2. Image forming apparatus according to claim 1 wherein said first drive means is a drive belt and said second drive means includes an image member drive roller for frictionally driving said image member, an image member drive output roller fixed with respect to said image member drive roller and rotatable therewith and having an outside diameter equal to that of said image member drive roller, an idler roller about which said drive belt is trained, said image member drive output roller being positioned to engage and frictionally drive said idler roller. 
     
     
       3. Image forming apparatus according to claim 1 further including an encoder positioned to monitor the angular position of said transfer drum and logic and control for controlling image formation on said image member in response to the angular position of said transfer drum. 
     
     
       4. Image forming apparatus according to claim 1, wherein said image member is an endless web including a seam and said image forming apparatus further includes means for sensing the position of said seam and a logic and control responsive to said sensing for controlling the formation of images on said belt without the overlap of an image with said seam. 
     
     
       5. An image forming apparatus comprising: an image member movable through an endless path,   means for forming a toner image on said image member,   transfer means movable through an endless path to bring a transfer surface through transfer relation with the image member, said transfer means including a rotatable transfer drum having an outside diameter which controls the speed of the transfer surface relative to the rotational speed of the drum, and   at least one layer of material which varies in at least one dimension in response to varying ambient conditions, and which in turn varies the outside diameter of said drum as said material dimension varies,     drive means for driving both said image member and said transfer means through their endless paths, said drive means including: a transfer drive member rotatable with said transfer drum and having an outside diameter equal to the outside diameter of the transfer drum,   a drive belt positioned around said transfer drive member,   means for driving said drive belt at a speed equal to the speed of said image member,     wherein the transfer drive member includes at least one layer of material which varies with ambient conditions sufficiently to maintain the outside diameter of the transfer drive member equal to the outside diameter of the transfer drum as ambient conditions vary.   
     
     
       6. Image forming apparatus according to claim 5 wherein said transfer surface is the outside surface of the transfer drum and is rotatable through transfer relation with the image member to receive a plurality of different color single-color images from said image member in registration to form a multicolor image. 
     
     
       7. Image forming apparatus according to claim 6 wherein said image member is an endless web trained about a plurality of image member rollers, at least one of said image member rollers being an image member drive roller which frictionally drives said image member. 
     
     
       8. Image forming apparatus according to claim 7 wherein said drive means further includes a web drive output roller affixed to said image member drive roller and having an outside diameter equal to that of said image member drive roller and an idler roller frictionally driven by said web drive output roller and wherein said drive belt is trained about said idler roller and said transfer drive member. 
     
     
       9. Image forming apparatus according to claim 6 wherein said layers of material in both said transfer drum and said transfer drive member that vary with ambient conditions are of equal thicknesses of the same material. 
     
     
       10. Image forming apparatus according to claim 5 wherein said image member is an endless belt trained about a plurality of image member rollers, at least one of said image member rollers being an image member drive roller which frictionally drives said image member. 
     
     
       11. Image forming apparatus according to claim 10 wherein said layers of material in both said transfer drum and said transfer drive member that vary with ambient conditions are of equal thicknesses of the same material. 
     
     
       12. Image forming apparatus according to claim 11 wherein said material expands with an increase in relative humidity. 
     
     
       13. Image forming apparatus according to claim 5 further including an encoder positioned to monitor the angular position of said transfer drum and logic and control for controlling image formation on said image member in response to the angular position of said transfer drum. 
     
     
       14. Image forming apparatus comprising: an endless web image member trained about a plurality of rollers for movement through an endless path,   means for forming a series of single-color toner images on said image member,   an intermediate transfer drum having an outside transfer surface rotatable through transfer relation with said image member and at least one layer of material which causes the outside diameter of the transfer surface to vary in response to varying ambient conditions,   a rotatable transfer drive member, fixed to or integral with said transfer drum, which drive member has a drive surface of the same outside diameter as the transfer surface and a layer of material of substantially the same thickness and response to ambient conditions as said at least one layer of the transfer drum,   drive means for driving both the image member and the transfer drum, said drive means including, an image member drive roller for frictionally engaging and driving said image member,   a web drive output roller fixed with respect to, rotatable with and having the same outside diameter as said image member drive roller,   an idler roller frictionally engaging and drivable by said web drive output roller,   a timing belt positioned around said transfer drive member and said idler roller for driving said transfer drive member and said transfer drum in response to rotation of said idler roller by said web drive output roller, and   means for rotating said image member drive roller and said web drive output roller to move both said image member and said transfer surface at the same speed.     
     
     
       15. Image forming apparatus according to claim 14 further including means for transferring said toner images in registration to said transfer surface to form a multicolor image and means for transferring said multicolor image to a receiving sheet.